Method fob the preparation of alpha



Patented Sept. 28, 1943 UNITED STA 2,330,791 s PATENT OFFICEI METHODFOR, THE PREPARATION OF ALPHA NABHTHOSELENAZOLES Edmund B. Middleton,Woo'dbridge, and George A.

. Dawson, Stelton, N. .L, assignors, by mesne assignments, to E. I. duRent de-Nemours & Company, Wilmington, Del., a corporation of DelawareNo Drawing. Application June 3, 1940,

Serial N0. 338,556 l 7 Claims. (Ci. 2601 -258) This invention relates toalpha naphthoselena zoles, more particularly Z-hydrocarbon alphanaphthoselenazole, and a method forthepreparation thereof,

I This application is a continuation-impart of 78,734,1"1led.

our copending application Serial No. May 8,. 1936.

Among theobjects of the invention are manufacture f alphanaphthoselenazoles, more particularly 2-hydrocarbon alpha naphthoselenazolesof high purity in good yieldsby aseries of reactions which proceedrather smoothly with a minimum of side reactions andat an economicahcost. These objects have not heretofore been.

The alpha napl1tl1oselenazoles,;and especially the 2-alkyl alphanaphthoselenazoles,. are, very. I,

salt with a selenocyanate in the-presence of an oxidizing, agent; (2)heating the resultant product with a strong hydrolysing agent; and. (3)treating thehydrolysisproduct with an acylating agent. The/final productmay be recovered in any convenient manner. l

Thehseries of reactions in question starting with ,beta naphthylaminemay-"be carried out in several different ways, as. follows;

A. The beta naphthylamine is converted in a well: known manner toal-halogenmZ-amino naphthalene salt. The amine saltlof the '1,halogeno-2-amino naphthalene is then reacted with aselenocyanate,preferably analkali metal selenocyanate such as potassium selenocyanate.The reaction product is preferably made alkaline with ammonia. Theresultant product is then hydrolysed, preferably by treatment withastrong alkaline solution such as a solution -of sodium hydroxide orpotassium hydroxide. The resultantproduct obtainedv upon hydrolysis isthen preferably oxidized, for example, by treatment with a dilutehydrogen peroxide solution. The oxidation product is preferablyseparated. It is then reduced and reacted with an acylating agent.

Thismaybe accomplished, for examp1e,"by carryingout the reaction withacetic anhydride in the presence of metallic zinc, thereby'producing aZ-methyl alpha naphthoselenazole.

pose should preferably be substantially inert to the free halogen. Thesolvent employed should also preferably be a solvent for both the betanaphthylamine} and the selenocyanate. although this.is,not-absolutelyessential. Itshould preferably be nonraoid since acid solvents precipitat e selenium: from certain selenocyanate comm, pounds. Itis,ordinarily preferable to employ a mixture of solvents because it hasbeen found that. in most instances one'solvent does not give thedesiredresults, Alcohols, such as, for example, ethyl alcohol, arecommon solvents for both beta naphthylamine and selenocyanates such asthe alkali metal selenocyanates. These: alcohols, ho-wevenarehalogenated by free halogens such as bromine. This'halogenation maybesubstantially avoided byemploying. a mixture of $01- vents suchas,,for example, a mixtureof an alcohol and sme ma solvent substantiallyinert to halogen.. Mention rnay be made particularly of .mixtures ofalcohol with halogenated hydrocar bons, 'e. g. chloroform and/0r carbontetrachlo ride.

' tion. .The product thus obtained is then reduced The product obtainedis preferably treatedwit ammonia. The resultant product is thenhydrolysed. with a strong alkaline solution. It may be isolated from thealkaline solution byoxidaand reacted with an acylating agent to producea 2-hydrocarbon alpha naphthoselenazole.

C. The betanaphthylamine is reacted directly with cupric selenocyanateinthe presence of a solvent. The reaction'product is extracted as a saltby treatment with a mineral acid. Treating the salt solution withammonia precipitates the free base. The resultant productis thenhydrolysed and the hydrolysis product is preferably isolated byoxidation, for example, with hydrogen B. The beta naphthylamine and-aselenocy anate in a suitable solvent are treated with a peroxide.Thefproduct thus isolated is then reduced and reacted with an acylatingagent to produce a 2-hydrojcarbfon alpha naphthoselenazole. I

"The 2-hydrocarbon alpha ,naphthoselenazoles thus produced havev thefollowing general formula:

in'which R represents a naphthalene nucleus, Se represents a seleniumatom attached to an alpha position of said naphthalene nucleus, Nrepresents a nitrogenatom attached to an adjoining beta position of saidnaphthalene nucleus, C represents a carbon atom between said seleniumatom and said nitrogen atom, and R1 represents hydrogen or a"hydrocarbon group; for example, an

5 alkyl group, as methyl, ethyl, propyl, or the like;

aryl, as, phenyl, tolyl, xylyl, naphthyl, diphenyl,

free halogen. A suitable solvent for this purthe particular acylatingagent employed in carrying out the reactions described. For instance; inorder to produce a Z-methyl alpha naphthoselenazole, acetic anhydride'isused*,"lorzacetyl" chloride. To produce a 2-ethyl alpha naphth'oselenazole, propionic anhydrideor propionyl chlo'-- ride is used. Inorder to produce 2'-:hydrocarbom2 aalpha naphthoselenazoles havingagreat-er or lesser number of carbon atoms; an acylating agent isemployed appropriate to the number of carbonatoms desired. For instance;the -lauryl" or the like;- aryl' alkyl,=.as; benzyl; cinnamyl. Thenature of the hydrocarbon groupiwill depend upon of alcohol was treatedwith: 28 parts of potassium selenocyanate-in 80 parts of Water. Afterstanding over night at room temperature, the mixture was evaporated todryness and extracted many times with hot water. The extract was madealkalineswith ammonia and the aminonaphthoselenazol'e precipitated. Itwas recrystallized from alcoholi Yield 36 parts; M. P. 252 C. Thiscompound has the formula:

derivative may be produced by using lauroyl chloe ride as the acylatingagent. The phenyl derivative may be produced by using benzoylchloride asthe acylating agent; and thecinnamylderiva tive' 'may lee-produced byemploying cinnamoyl.

chloride asith'e' acylating agent. Similarly other acylatingagents of'the type described are-zem' The radical R may containisubstituentgroup's-.-= Among such groups -are; for example, halogen (eag.-chlorine, bromine; iodine; fluorine)"; alkyl (e. g. meth yL ethyl,propylg butyl i and higher homologues) and alkoxy (e: g: methoxy',ethoxy and higher homologues); It is essentiaL-however, for the" purposeof the present inventionthat the starting-"material be a betanaphthylainine in whichthe-alphaposition which is eventually-tobelinkedtoa selenium atom be eit'her unoccupiedor occupi'edbyahalogenatom.-- The'betapo'si ti'on-will naturally be occupied by an"amino group; It has been found 'thatbyusing' thesestarting-'materials-and proceeding inthe manner described difficultiesare avoided which ordinarilyare encountered in other proposed-processessuch as -those "involving the; use'of alpha naphthyl amineas astartingmaterial followed by nitra tion, diazotization, etc.

The compounds given in-Formulalare refrred" to herein" as' the'2-h'ydrocarbon' alpha naphthoselenazolebases.' These bases react withvorganic esters of organic and-inorganic "acids"to form"quaternaryamnronium salts. Among the esters'whichmay'be reacted .with these basesin" order to produce such" quaternary ammoniumsaltsare; for example;methyl chloride; ethyl chloride'and higheralkyl homologues, methyl dyes,dicarbocyanine dyes and other types of dyes.

Many of these dyes are useful in'making phot'o-.

graphic emulsions, particularly'as SBHSitlZGISJlII' such emulsions. Thecarbocyanine dyes are es-=' pecially valuable as green blind redsensitizers; that is to say, they sensitize in the red region of thespectrum but for photographic purposes are substantially insensitive inthe green reg-ion of the spectrum.

The inventi'on will be further illustrated but is not-=limited by thefollowin'g examples in which"; 70

- bined ifiltrateszwere :neutralizedmwithii ammonia and: theeaminonaphthoselenazole precipitated; TheoVeraILyield was substantiallylower than in the quantities are stated in parts by weight;

7 Example .I

A solution of 51 parts of..the.hydrochloride of 1 bitomo-Zaminonaphthalene in. about. 70 parts I ployed=t'o;pnoduce other aiphanaphthoselenazoles.

mixture .aofv 28iiparts1: of: the aminonaphthoselenazol'c; 28 partsofsodium hydroxide and 50 parts of water washeated together in a-nickelcrucibla-for-three hours on an electric hot plate.

Theizcoverrof the crucible was adjusted so that steam could escape.Water lost by evaporation wasreplacedas it boil'ed off. Finally thecrucible was evaporated to dryness and heated untilthe fum'es dueto-decomposition' began to appear.

llie r'esidue wastakem up with water and filtered. The filtratewasfcooled.and dilute hydrogen peroxide added drop b'y -dr'op'until' nomore precipitation =formed? The precipitated diselenide; a

i yellow amorphous powder, was separated by filtratioirawashed and"'dried;f A- yield -of 13 parts was obtained? This compound has the formula:

This was heated-toboiling in-108 parts of acetic anhydride i-underrareflux condenser "and '4 parts of zincgraduallyiaddeds Heating was.continued fonthirty:minutes-.- The hot solution wasfilteredfromsome-unreacted zinc; and poured'into water.

The solution. was laterextractedtavith ether; and

after :dryingethe V ether solution and removing the i ether-z by;-evaporation,.: needle crystals of the I 2 methyl alphanaphthoselenazolefi were obtained;: -It melted\ at Z81 F829a Yield-7'-parts.

On heating thecrude-material;with'three timesthe calculatedrquantityofxethyl iodide under reflux:foretwenty.-four .hours and Jthenevaporating Example II 3 withn47-.8 DaItSJOfLCUDI'iC :selenocyanate.:After heatingzunder. airefiuxicondensenfor fifteenminutes-.:about:30-.pants of :33% .Hl'.vvereadded and the: heatingwas.:continueddforrfifteen. minutes longer: Thezsolution:wascfilteredihbt and the residue washedaweil:iwithihot waterx. The comExample I. The-.compound:-.was .converted to methybnaphthoselenazole-asin ExampleI.

, Example III I Twenty-five (25) parts of beta'-jnaphthylamine and 13.8parts of potassium selenocyanate were dissolved in about '80 parts "ofalcohol[ in a 3-necked flask, equipped with a stirrer. The temperaturewas'fkept below 25 C. while. a solution form was'added dropby drop. Theflaskwa'sthen allowed to staiid at room temperature for severallioursafterwliich it was brought to a boil for arninut'e and then'allowed' 'to stand at room temperature fontwelve hours. The solutionwas diluted with several volumes of cold water and oil separated whichon standing deposited creamcolored crystals. These were filtered andrecrystallized from alcohol, about 7.5 parts of 1 rri j v .f .Ewample IVcarbricyanine dye was obtainedras follows: One-r1) "part of the-'ethiodidemade "as de- I scribed inExample I and 6 parts of dry pyridineand about 1 part of ethyl orthoforinate were heated-under reflux fortwentyminutes. An intense blue color developed)" On cooling, the dye wasobtained as beautiful greenish-gold crystals. This dye, sym-3 3'-diethyl-naphthoselenocarbocyanine iodide, has the structure CzHs It isa red sensitizer for a photographic emulsion. When dissolved in alcoholand added to a negative emulsion, it conferred extra sensitivity withmaximum at approximately 665: m. u. and extending to 700 m. u. g

In a manner similar to that described in Examples I, II and III, other.Z-allzyl-naphthoselenazoles and their quaternary salts may be prepared.For instance, the naphthalene nucleus may contain non-reactivesubstituents, e. g. alkyl (methyl, ethyl, propyl, and higher homologues)or alkoxy radicals (methoxy, ethoxy, and higher homologues) in one ormore of the 3-, 4-, 5-, 6-, 7- or 8-positions. It will be understood, ofcourse, that the ring closing positions of the beta naphthylamineinitially employed must be free of substituents. The expression betanaphthylamine in the form of a salt is intended to include and cover anamine salt of beta naphthylamine either as pre-formed or as formed insitu during a reaction. In carrying out the first step of the reactionusing an alkali metal selenocyanate, a non-acid medium is preferablyemployed because it has been found that the presence of an acid causesthe precipitation of selenium. It will be understood, however, that ifthe beta naphthylamine is present as amsalt, it is substantiallynon-acid. The reaction between the salt of the beta naphthylamine, as,for example, a hydrohalide salt, and an alkali metal selenocyanate, as,for example, potassium selenocyanate, results in the elimination of analkali of 28 parts ofbromine in about 45 parts of chlorohydrolysingbase.

metal halide and in the formation of a selenourea which may beisolatedfor purification if desired. In the presence of an oxidizingagent the formation of the seleno-urea is apparently merely transitoryand the product immediately obtained is a Z-amino alpha'naphthoselenazole. The oxidizing agent may be a halogen atom which isalready attached to the naphthylamine nucleus adjacent the amino group,as in Example. I, or it may be a free halogen added contemporaneously orsimultaneously, asin Example II. In either event a ring closureoccurs..Other oxidizing agents may be employed inthis step of the process, as,for instance, potassium ferricyanide, hydrogen peroxide, or potassium,permanganate. The salt, of Z-amino alpha naphthoselenazole willordinarily separate directly and if desired may beemployed directly inthe second or hydrolysis step of the process. It is ordinarilypreferable, however, to convert this salt to the freebase byneutralization with ammonia .or some other non- In carrying out thefirst step of the process any known selenocyanate may be used, althoughthe alkali metal selenocyanates are preferred, e. g. sodium andpotassium seleno-- cyanatesa If cupric selenocyanate is employed, it ispreferabletouseit in an organic solvent; For this purpose glacial aceticacidmay be used, although other solvents may be employed. i

i In carrying out the secondstep of;the process,

any-strong hydrolysing agent may be employed,

dium,

for example, solutions. of sodium hydroxide, potassium hydroxide ormixtures thereof. The hydrolysis actioncauses the selenazole ring of theZ-amino .alpha naphthoselenazole to be broken, thereby forming aselenonaphthol, .The selenonaphthol may be reacted directly with anacylating agent as, for example, an acid anhydride or an acid halide ofthe types previously mentioned. In this event a substantial excess ofacylating agent will be required in order to neutralize the akalinehydrolysing agent which is still present.

For this reason and in order to further purify the intermediate productbefore carrying out the final step, it is often desirable to oxidize theselenonaphthol to a diselenide, which can be separated as such andpurified. This may be accomplished by hydrogen peroxide, air, oxygen, orother oxidizing agents. If the selenonaphthol is oxidized to thediselem'de, the latter must be again reduced to the selenonaphtholbefore reaction with the acylating agent will take place. This reductionis accomplished by the use of nascent hydrogen, or any other suitablereducing agent. It maybe accomplished, for example, by adding metalliczinc to an acid acylating medium. The use of an acid halide, as, forexample, an acid chloride as the acylating medium is particularlydesirable because it can be added directly to the hydrolysis reactionproduct without requiring a large excess to neutralize the alkalipresent. This also results in the elimination of the diselenideformation step where the purpose or" this step is to eliminate thealkaline medium.

Having thus described the invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

1. In a method of making a 2-alkyl alphanaphthoselenazole, the series ofsteps which comprises (1) reacting beta naphthylamine in an acid solventmedium with copper selenocyanate, (2) heating the reaction mixture in anacid me- (3) neutralizing the resultant reaction mixture with ammoniaand separating the precipitate, l) heating said precipitate with astrong Y alkaline hydrolysingcagen-t: v(5) treating theihye'drolysisiproductwith. an oxidizing agent and separating .the-Vprecipitategw) heating saidprecipitate with a' lower aliphatic"carboxylic. acid anhydride in the presence-of. nascent hydrogen andseparating the -resultant -2-'alk yl alpha naph- V thoselenazole; t v

2. In a method of making; 2-methy1'- alpha naphthoselenazoles; theseriestof steps which comprises (1) reacting beta naphthylaminewinglacialiaceticlacid with copper selenocyanate; v(2) refluxing :theireacti'onsmixture with hydro-- chloric acid; (3 neutralizing withram-monia and 2 separating the resultant precipitate, .(4 heating. saidprecipitate with a strong caustio alkali solution, (5) treatingltheresulting -iproduct'iwith an. oxidizing agent and separating theprecipitate;

6) heating said precipitate acetic: 8111 1137: dride in the presence ofzinc and. separating the resultant 5 Q-methyl alpha naDhthoselenazole;

3; In amethod of making ay;2-a1kyl alpha naphthoselenazole, the seriesof steps which comprises (1) a contemporaneously" reacting betanaphthylamine, an alkali metal selenocyanate and afree halogen andheating the reaction mixture, (2) neutralizing and-separating theprecipitate, (3) heatingthe precipitate with a strongalkalinehydrolysing agent; v(4) treating the hydrolysis product with anoxidizing l agent andseparating the resultant precipitate; and (5)heating said precipitate with-a lower.- aliphatic carboxylic' acidanhydride inthe presence ofo nascent hydrogen.

tion, (5) treating therhydrolysis product with hydrogenrperoxide andseparating the precipitate; (6)" heating said precipitate withaceti'canhydride1n .the presence of zinc and separatmg the 2:-methy1.a1phanaphthoselenazole."

51The"m'eth'od' of preparing 2-"alkyl-a1phanaphthoselenazoles whichcomprises treating a betanaphthylamine in -the form of a salt with a'selenocyanate "under oxidizing conditions, hydroly'zing"thepxidationproduct with'an alkali; oxidizing the hydrolysis product; v.treatir'ig'the insoluble oxidation product with 'an acylating' agent and reducingit with nascent hydrogen;

6. .In a. method. of making aZ-a'llyl-alphanaphthoselenazole;theiserie's 'ofsteps which comprises treatinga beta'naphthylamine'in theform of a salt witlfa metallic, selenocyan'ate 'in'th'e presence of'a"free halogen and inth'e presence of "a substantially. non-acid. organicsolvent which issubsta'ntially inert to the free halogen, toform' aZQamino alpha-naphthoselenazole; heating the 2famino-a1phanaphthoselnazole with a strong hydrolyzing' agent,"cxidiz'in'g thehydrolysis product, reducing the insoluble oxidation product with"nascent hydrogen, and adding an 'acylating agent.

'7. In method: of making" a 2-alky1-alphanaphthoselenazole, the seriesofsteps which comprises treatinga beta'naph'thylamine in the form of asalt and unsubstituted-in the alpha position with a metallicselenocyanate and 'a freehalogen in a mixture vof substantially,non-acid organic solvents, at least one of said solvents being a commonsolvent-for bot-h the-beta naphthylamine and the selenocyanateandanotherbeing a-solvent for said free halogen and substantially inertthereto, to form a 2-amin0-alpha-naphthoselenazole, heating the"2-amino-alpha-naphthoselenazole with-a strong hydrolyzing agent,oxidizing the hydrolysis product} reducing the insoluble oxidationproduct with nascenthydr'ogen, and treating with an acylating agent. I

EDMUND B. MIDDLETON. GEORGE A. DAWSON.

